Tool for drilling or boring metals



I]. W. LITCHFIELD TOOL' F63 DRILLING" JR BORING METALS Filed Oct. 7.1920 Z Sheets$heet 1.

7 l. w LBTCHFIELD TOOL FOR DRILLING OR BORING METALS Filmed OGt. V. 1920i Sheelm-Shwmfi. 2

Patented duty T, iaaa ISAAU W. LITGHEIELD, 01E NEWTONVILLE,MASSACHUSETTS.

TOOL FOR DRILLING OR BORING METALS.

Application filed October 7, 1920. Serial No. 415,429.

To all whom it may concem:

Be it known that 1, Isaac W. LITOHFIELD,

a citizen of the United States, and a resident of Newtonville,Massachusetts, have invented new and useful Improvements in Tools forDrilling or Boring Metals, which invention is fully set forth inthefollowing specification.

This invention relates to tools for drilling metal, and it has for anobject to pro vide a tool of this character which will operate withgreater speed and higher efliciency than tools heretofore provided.

The conventional twist drill, owing to the length of its cutting edge,is in reality more of a scraper than a cutter in operation, whereby itsprogress through the metal s necessarily slow. To obviate this defect ithas heretofore been suggested to notch the cutting edges of a twistdrill, the notches 1n one cutting edge being staggered with respect tothe notches in the other cutting edge so that the following cuttlng edgeWlll cut off the ridges left by the notches in the advancing cuttingedge. Tools of this character are exceedingly dificult to sharpen asthey require special grinders and, ow ng to the different spacing of thenotches in the two edges, separate grinders for each edge are necessary.

It is an object of this invention to .pro vide a tool for drilling metalwhich operates more nearly as a cutter While, at the same time, avoidingdifliculties heretofore experienced in notching the edges of twistdrills.

Another object of this invention is to provide a tool for drilling metalwhich is provided with an interrupted cutting edge and an uninterruptedcutting edge adapted to follow said interrupted cutting edge and cut offthe ridges left by the interruptions therein, said uninterrupted cuttingedge being positioned axially to the rear of the interrupted cuttingedge so as to produce a balanced cut.

Another object of this invention is to provide a tool of the typecharacterized with a pilot portion whereby the tool may be accuratelycentered or the metal at the axis removed.

Another object of the invention is to provide a tool of the typecharacterized with a removable cutter portion whereby the shank portionmay be made of a lower grade of steel than required for the cuttingedges and whereby the cutters may be readily withdrawn for resharpeningor replacement.

Another object of the invention is to provide the shank of a tool of thetype characterized with means to facilitate the egress of the chips.Other objects will appear as the description of the invention proceeds.

Stated broadly, the invention'comprises a tool for drilling metal havingan interrupted cutting edge and an uninterrupted cutting edge adapted tofollow said first-mentioned edge and remove the ridges left by theinterruptions therein, said uninterrupted cutting edge being positionedaxially to the rear of said interrupted cutting edge sufficiently tobalance the amounts of metal which will be removed by the respectivecutting edges. Said cutting edges are preferably provided on removablecutters suitably held in position in a shank portion, said shank portiondesirably being provided with flutes to facilitate the egress of chips.Said tool may be provided with a pilot portion projecting forwardly inthe axis of the tool either to guide the progress of the tool when acentering hole has first been provided or to drill a hole in advance ofthe main cutting edges and remove the metal at the axis-in advance ofthe latter.

The invention is capable of receiving a variety of mechanicalexpressions some of which are shown on the accompanying drawings, but itis to be expressly understood that the drawings are for purposes ofillustration only and are not to be construed as a-definition of thelimits of the invention, reference being had to the appended claims forthat purpose.

In said drawings, wherein the same reference characters are employed todesignate corresponding parts in the several figures Fig. 1 is anelevation of a tool for drilling metal constructed in accordance withthe present invention;

Fig. 2 is an enlarged end view thereof;

Fig. 3 is an enlarged side view of said tool looking in the direction ofthe interrupted cutting edge;

Fig. 4 is an enlarged side view of said tool looking in the direction ofthe uninter rupted cutting edge;

Fig. 5 is an enlarged side view of an embodiment of the presentinvention wherein both of the cutting edges are inclined to the axis ofthe tool;

Fig. 6 is an enlarged side view of an embodiment of the present invent1on wherein only one of the cutting edges is mchned to the axis of thetool;

Fig. 7 is an elevation of another embodi said last-named figure.

In the form shown in Figs. 1 to 4 the drill comprises a shank portion 1,suitably formed, as shown at 2, to fit mto any desired tool holder, andprovidedat its end with two cutting ed es 3 and 4, the former of whichis provi ed with interruptlons and the latter of which is uninterrupted.In the embodiment illustrated, the interrupted cutting edge is providedby forming notches 5 in said edge so as to give the appearance of aplurality of teeth. The uninterrupted cutting edge is positioned axiallyto the rear of the interrupted cutting edge so as to remove the ridgesleft by the interdental spaces of the cutting edge 3. The distance towhich the line of the uninterrupted cutting edge is positioned to therear of the line of the interrupted; cutting edge will vary slightlywith difl'erent metals to be operated upon and diflferent sizes andspeeds of the tool, but I have found that 1/64 of an inch to 1/32 of aninch is a suitable spacing of said cutting edges. The cutting edgeswhich thereby have the capacity of doing substantially the same amountof work by removing substantially equal amounts of metal are ground toprovide a suitable clearance and their advancing faces are preferablyplain surfaces having-a suitable rake.

In order to facilitate sharpening of the cutting edges and to enablereplacement when badly worn, the cutting edges are preferably providedon removable cutters 6 and 7, in which event the shank 1 may be made oflow grade steel. The removable cutters 6 and 7 may be held in positionin any suitable way. In the form shown, the shank 1 is provided in itsend with a transverse groove 8 having an undercut extension 9 and thecutters are shaped to interlock in the groove so formed. It is to beexpressly understood, however, that the groove and cutters may be ofdove-tailed or any other suitable shape adapted to retain the cutterssecurely in po- 7 sit1on.-

" The tool of the present invention may also be provided with a pilotportion 10 .which in turn may .be either a plain pilot 1port1on tseeFig. 9) projecting forwardly "in the axls of the tool for engagement ina .previously formed hole tocenter and guide the progress of the tool,or a pilot drill that w1ll itself form a pilot hole in advance of thetool. Said pilot portion is preferably madaremovable and may be retainedin position in any suitable Way. The head of said pilot ortion ispreferably provided with a shou der 11 which is adapted to overhang theinner ends of the cutting edges so as to prevent the formation of a finat the junction of the cutting edges and the pilot portion.

To facilitate the egress of chi s the shank 1 may be provided withspiral utes 12 and the entrance to said flutes may be so sha ed as toprovide a shoulder or bafile 13 agalnst which the chips will impinge andbecome broken.

In the embodiment of Figs. 1 to 4 the two cutting edges are positionedso that they lie'at right angles to the axis of the tool. This is notessential, however, as one or both of the cuttingedges may be inclinedeither inwardly or outwardly with respect to the axis of the tool. Inthe embodiment of Fig. 5 both cutting edges are inclined outwardly withrespect to the axis of the tool while in the embodiment of Fig. 6 theuninterru ted cutting edge is inclined inwardly with respect to the axisof the tool. In both of these latter embodiments it will be perceivedthat the uninterrupted cutting edge is positioned axially to the rear ofthe interrupted cutting edge, and in the embodiment of Fig. 5 (as in theembodiment of Figs. 1 to 4) the surface described by the uninterruptedcutting edge lies parallel to but axially at the rear of the surfacedescribed by the interrupted cutting ed e.

In the embodiment of Figs. 7 to 9 t e tool is provided with a flattenedhead 14 havin a longitudinal oove in which the inserted cuttersinterlock? Said cutters may be retained against longitudinaldisplacement in said grooves by pointed screws 15, received .in threadedapertures in said head 14, and

projecting into engagement with said outters. Instead of providing theshank with flutes it may be reduced in diameter as shown at 16 toprovide a clearance for the egress of chips.

It will therefore be perceived that I have provided a tool for drillingmetal which will operate as a cutter, the same having an interruptedcutting edge and an uninterrupted cutting edge positloned axially to therear of said interrupted cutting edge and thus adapted to follow andremove the ridges left by said interrupted cutting edge while at thesame time providin a balanced cut. It will also be perceived tiat I haveprovided a tool a just characterized whereby the shank ma be made of lowgrade steel and the cutters may be readily inserted and withdrawn forregrinding or replacement. Furthermore, the tool, if desired, may beprovided with either a lain or a drilling pilot to center and gui e thetool and remove the metal at the axis, particularly it of a large size.Also the shank of the tool is so constructed as to facilitate the.egress of chips, which may be broken up immediately after leaving thecutting edges.

While the embodiments of the invention shown on the drawings have beendescribed with considerable particularity it is to be expresslyunderstood that the invention is not limited to'the same as it iscapable of receiving a variety of mechanical expressions some of whichwill be now readily suggested to those skilled in the art. Changes mayalso be made in details of construction and arrangement of parts withoutde arting from the spirit of this invention. eference is therefore to behad to the claims hereto appended for a definition of the limits of saidinvention.

What is claimed is:

1. A drill having an interrupted cutting edge and an uninterruptedcutting edge adapted to follow said interrupted cutting edge and removethe ridges left by the interruptions therein, the uninterrupted cuttingedge being axially to the rear of said interrupted cutting edgesufliciently to produce a balanced cut.

2. A drill having an interrupted cutting edge and an uninterruptedcutting edge adapted to follow said interrupted cutting edge and removethe ridges left by the interruptions therein, the uninterrupted cuttingedge being axially to the rear of said interrupted cutting ed esufiiciently to produce a balanced cut an at least one of said cuttingedges being inclined to the axis of the drill. o

3. A drill having a notched cutting ed e and a strai ht cutting edgeaxially to t e rear of sai notched cutting edge and so positioned thatthe efiective length of the straight cuttin edge is approximately equalto the efiective ength of the notched edge;

4. A drill having an interrupted cutting tlti edge, an uninterruptedcuttin edge axially to the rear of said interrupte cutting edgesufliciently to a pilot projectlng forwardly in the axis of the drilland ada ted to form a central hole in advance of said cutting edges.

5. A drill having a notched cutting edge, a straight cutting edgeaxially to the rear of said notched cutting edge and so positioned thatthe efiective length of the straight cutting edge is approximately equalto the efiective length of the notched cutting edge, and a pilotprojecting forwardly in the axis of the drill.

6-. A drill having a shank provided with a transverse groove in the endthereof and removable cutters in said groove, said groove and cuttersbeing formed to provide an interlock, one of said cutters having aninterrupted cutting edge and the other of said cutters having anuninterrupted cutting edge adapted to follow said interrupted cuttingedge, said uninterrupted cutting edge being axially to the rear of saidinterrupted cutting edge.

7. A drill having an interrupted cutting edge and an uninterruptedcutting edge axlally to the rear of said interrupted cutting edgesufliciently to do substantially the same amount of work in removingmetal as is done by said interrupted cutting edge.

8. A drill having an interrupted cutting edge, an uninterrupted cuttinedge axially to the rear of said interrupte cutting edge sufliciently todo substantially the same amount of work in removing metal as is done bysaid interrupted cutting edge and a giltit projecting forwardly in theaxis of the In testimony whereof l have signed this specification.

rso w. mrenrrntn.

produce a balanced cut, and

